Differential seedling performance and environmental correlates in shrub canopy vs interspace microsites
2012
Boyd, C. S. | Davies, K. W.
Shrubs in semi-arid ecosystems promote micro-environmental variation in a variety of soil properties. We compared post-fire seeding success and soil variables between shrub (“under-canopy”) and interspace locations for hand-seeded bluebunch wheatgrass (Pseudoroegneria spicata) and crested wheatgrass (Agropyron cristatum) in Wyoming big sagebrush (Artemisia tridentata) plant communities in southeast Oregon, U.S.A. We burned 5, 20 x 20 m sites in October, 2009 and established paired under-canopy and interspace micro-transects. Transects were seeded to bluebunch wheatgrass (193 seeds/m) or crested wheatgrass (177 seeds/m). We monitored seedling density in 2010, and measured soil-related environmental variables. Seedling density was 69% higher for crested wheatgrass and 75% higher for interspace locations. Decreased density in under-canopy was associated with wind erosion of seeds. Tiller and leaf area production were over twice as high (p < 0.05) in under-canopy locations. Six of 24 soil variables differed (p < 0.10) between locations. These six variables, particularly soil color and soil temperature, explained 19 - 32% of variation in seedling performance. Shrub effects on seeding success are complex and interact with abiotic disturbances, but patterns of increased seedling performance in under-canopy locations and their relationships to soil variables may suggest tactics for increasing success of restoration practices.
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